TW201634494A - Film - Google Patents

Abstract

Provided are a film that makes it possible to easily produce an optical film having exceptional optical properties, durability, and reduced shrinkage, and a method for producing an optical film in which said film is used. A film containing a hydroxymethyl group-containing vinyl alcohol polymer having a 1,2-glycol bond content of 1.5 mol% or less, including vinyl alcohol units and the structural units shown by formula (1); and a method for producing an optical film having a step for uniaxial stretching using this film.

Description

film

The present invention relates to a film comprising a specific hydroxymethyl group-containing vinyl alcohol polymer having a 1,3-diol structure, and a method for producing an optical film using the same, and as an optical film for producing a polarizing film. The germplasm film is useful.

A polarizing plate having a function of penetrating and shielding light is a basic constituent element of a liquid crystal display (LCD) as a liquid crystal that changes a polarization state of light. In order to prevent fading of the polarizing film or to prevent shrinkage of the polarizing film, most of the polarizing plates have a structure in which a protective film such as a cellulose triacetate (TAC) film is bonded to the surface of the polarizing film, and a polarizing film constituting the polarizing plate is formed. In the case where a vinyl alcohol polymer film (hereinafter, "vinyl alcohol polymer" is sometimes referred to as "PVA") is uniaxially stretched, an iodine dye (I ₃ ^- and I) is adsorbed. ₅ ^-etc .) or dichroic dyes such as dichroic organic dyes have become mainstream.

LCD has gradually been transformed into a wide range of small machines such as computers and watches, mobile phones, notebook computers, LCD monitors, liquid crystal color projectors, LCD TVs, car navigation systems, and metering machines that can be used indoors and outdoors. In recent years, in particular, thinness and light weight have been required. The thinning of the components of the LCD has also progressed, accompanied by When the polarizing plate protective film is made thinner, there is a concern that the function of preventing fading of the polarizing film is lowered, or the function of preventing shrinkage of the polarizing film is lowered. Then, a polarizing film which can maintain shrinkage, high transmittance, and excellent optical characteristics while reducing fading and having excellent durability while reducing shrinkage is being sought.

Incidentally, several blanks for producing an optical film for producing a modified PVA are known. For example, it is known that a polyvinyl alcohol film for a preform material comprising a polarizing film composed of a specific PVA having a hydrophilic functional group such as 0.01 to 1 mol% of a carboxylic acid group or a ω-hydroxy-α-olefin group is pulled. The coating treatment property and the dichroic substance are excellent in the adsorption treatment property, and exhibit excellent optical properties (see Patent Document 1, etc.). Further, it is known that a specific optical PVA film comprising a specific PVA having a 1,2-diol bond in a side lock is excellent in optical properties and stretchability (see Patent Document 2).

[Previous Technical Literature] [Patent Literature]

Patent Document 1: Japanese Patent Publication No. 8-201626

Patent Document 2: Japanese Laid-Open Patent Publication No. 2009-24076

However, when a preform material for optical film production using a conventional modified PVA is used, there is still room for improvement in terms of obtaining an optical film excellent in optical characteristics, durability, and shrinkage reduction.

Accordingly, it is an object of the present invention to provide a film, and a method of producing an optical film using the same, which can be easily fabricated An optical film excellent in optical properties, durability, and shrinkage reduction.

In order to achieve the above object, the present inventors have repeatedly conducted intensive investigations and found that the above problems can be solved in accordance with a film, and the present invention has been further studied based on the knowledge, and the film comprises the following PVA containing a methylol group. The hydroxymethyl group-containing PVA contains a specific structural unit having a 1,3-diol structure in the main chain, and the 1,2-glycol bond amount is in a specific range.

That is, the present invention relates to:

[1] A film comprising the following hydroxymethyl group-containing PVA, wherein the hydroxymethyl group-containing PVA comprises a vinyl alcohol unit, and a structural unit represented by the following formula (1), and a 1,2-glycol bond The amount of the knot is 1.5 mol% or less.

[2] The film according to [1], wherein the content of the structural unit represented by the above formula (1) in the hydroxymethyl group-containing PVA is 0.1 to 2 mol%;

[3] The film according to [1] or [2] wherein the hydroxymethyl group-containing PVA has a degree of saponification of 95 mol% or more;

[4] The film according to any one of [1] to [3] which is a raw material film for optical film production;

[5] The film according to [4], wherein the optical film is a polarizing film;

[6] A method for producing an optical film, which comprises the step of uniaxially stretching using the film according to [4] or [5].

According to the present invention, it is possible to provide a film and a method for producing an optical film using the same, which can easily produce an optical film excellent in optical characteristics, durability, and shrinkage reduction.

[Formation of the Invention]

The film of the present invention comprising the following hydroxymethyl group-containing PVA comprising a vinyl alcohol unit, a structural unit represented by the following formula (1), and a 1,2-glycol bond The amount is 1.5 mol% or less.

In the film of the present invention, since the PVA containing a methylol group contains a structural unit having a 1,3-diol structure represented by the above formula (1), the stretchability is improved, and the film according to the present invention is improved. That is, an optical film excellent in optical characteristics can be easily produced. Further, it has a feature of reducing the contraction force of the optical film. For the reasons for the above advantages It is considered that the structural unit represented by the formula (1) lowers the crystallinity and the influence of the high hydrogen bonding force based on the 1,3-diol structure, but it is not a limitation of the present invention.

In the PVA containing a methylol group, the content of the structural unit represented by the formula (1) is not particularly limited, but the molar number of all the structural units constituting the PVA containing a methylol group is 100 mol%. It is preferably in the range of 0.1 to 2 mol%, more preferably in the range of 0.2 to 1.9 mol%, and still more preferably in the range of 0.3 to 1.8 mol%. When the content is 0.1 mol% or more, the stretchability of the film is further improved, and an optical film which is more excellent in reducing the shrinkage force can be obtained. On the other hand, when the content is 2 mol% or less, the dissolution of the film during the production of the optical film can be more effectively prevented, and an optical film having more excellent optical characteristics can be obtained. In the present specification, the term "structural unit" means a repeating unit constituting a polymer.

In addition, when the amount of the 1,2-glycol bond of the PVA containing a methyl group is 1.5 mol% or less, an optical film having less fading and excellent durability can be obtained. The amount of the 1,2-diol bond is preferably 1.4 mol% or less, more preferably 1.2 mol% or less, and still more preferably 1.0 mol% or less. The lower the amount of the 1,2-glycol bond, the better the durability of the obtained polarizing film.

Further, by using the vinyl ester monomer at a temperature lower than 50 ° C, preferably lower than 40 ° C, more preferably lower than 30 ° C, still more preferably lower than 20 ° C, particularly preferably lower than 5 ° C By polymerization, it is possible to easily produce a modified PVA having a 1,2-diol bond amount within the above range. From the viewpoint of the polymerization rate of the vinyl ester monomer, the lower limit of the industrially possible polymerization temperature is about -50 ° C. From this viewpoint, the 1,2-diol bond amount of the PVA containing a methylol group. Lower limit The limit is about 0.5 mol%. The 1,2-glycol linkage amount of the hydroxymethyl group-containing PVA can be determined by a conventional NMR measurement.

The degree of polymerization of the hydroxymethyl group-containing PVA is preferably in the range of 1,500 to 6,000, more preferably in the range of 1,800 to 5,000, and still more preferably in the range of 2,000 to 4,000. By the degree of polymerization of 1,500 or more, the durability of an optical film such as a polarizing film obtained by uniaxially stretching a film can be improved. On the other hand, when the degree of polymerization is 6,000 or less, it is possible to suppress an increase in the production cost and a failure in the passability at the time of film formation. In addition, the degree of polymerization of the hydroxymethyl group-containing PVA in the present specification means the average degree of polymerization measured according to the description of JIS K6726-1994.

The saponification degree of the PVA containing a methylol group is preferably 95 mol% or more, more preferably 96 mol% or more, from the viewpoint of water resistance of an optical film such as a polarizing film obtained by uniaxially stretching a film. , and then better than 98% Mo. Further, the degree of saponification of the hydroxymethyl group-containing PVA in the present specification means that it can be converted into a vinyl alcohol unit (-CH ₂ -CH(OH) with respect to saponification of a hydroxymethyl group-containing PVA. - The ratio of the molar number of the vinyl alcohol unit (% by mole) of the structural unit (typically the vinyl ester unit) to the total number of moles of the vinyl alcohol unit. The degree of saponification can be measured in accordance with the description of JIS K6726-1994 after considering the amount of the structural unit represented by the formula (1) and its derivative.

The method for producing the PVA containing a methylol group is not particularly limited. For example, a method in which a vinyl ester monomer and an unsaturated monomer copolymerizable therewith and which can be converted into a structural unit represented by the formula (1) are copolymerized, and the obtained vinyl ester copolymer is copolymerized Vinyl ester unit conversion It is a vinyl alcohol unit, and on the other hand, a structural unit derived from an unsaturated monomer which can be converted into a structural unit represented by the formula (1) is converted into a structural unit represented by the formula (1). A specific example of the unsaturated monomer which can be converted into the structural unit represented by the formula (1) is shown in the following formula (2).

In the formula (2), R represents an alkyl group having 1 to 10 carbon atoms. The structure of R is not particularly limited, and may have a branched or cyclic structure in one portion. Alternatively, it may be partially replaced by other functional groups. R is preferably an alkyl group having 1 to 5 carbon atoms, and examples of the alkyl group include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, and tertiary butyl group. A straight chain or a branched alkyl group such as a pentyl group or a pentyl group. Further, examples of the substituent which R may have include an alkoxy group, a halogen atom, a hydroxyl group and the like. Furthermore, there are a plurality of Rs which may be the same or different from each other.

The unsaturated monomer represented by the formula (2) may, for example, be 1,3-diethoxycarbonyl-2-methylenepropane or 1,3-dipropenyloxy-2-arylene. Methylpropane, 1,3-dibutyloxy-2-methylenepropane, and the like. Among them, 1,3-diethyloxy-2-methylenepropane is preferably used in terms of ease of manufacture.

The unsaturated monomer represented by the formula (2) is more easily reacted with the vinyl ester than the other allyl type unsaturated monomer (for example, allyl glycidyl ether or the like) which is generally used for modification of PVA. Monomer copolymerization. Therefore, there is little restriction on the amount of modification and the degree of polymerization at the time of polymerization, and a PVA containing a methyl group having a modified amount and a high degree of polymerization can be easily obtained. Further, since the amount of the unreacted unsaturated monomer remaining at the end of the polymerization can be reduced, the PVA containing a methylol group in the present invention is also excellent in the environmental surface and the cost side at the time of industrial production. .

The vinyl ester monomer used for the production of the PVA containing a methylol group is not particularly limited, and examples thereof include vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, and the like. Methyl vinyl acetate, vinyl versatate, vinyl hexanoate, vinyl octanoate, vinyl phthalate, vinyl laurate, vinyl palmitate, vinyl stearate, vinyl oleate, vinyl benzoate Wait. From the viewpoint of economy, vinyl acetate is preferred.

The polymerization method in which the unsaturated monomer represented by the formula (2) and the vinyl ester monomer are copolymerized may be any one of batch polymerization, semi-batch polymerization, continuous polymerization, semi-continuous polymerization, and the like. As the polymerization method, a conventional method such as a bulk polymerization method, a solution polymerization method, a suspension polymerization method, or an emulsion polymerization method can be applied. Generally, a bulk polymerization method or a solution polymerization method in which polymerization is carried out in a solvent-free or solvent such as an alcohol is employed. In order to obtain a vinyl ester copolymer having a high degree of polymerization, an emulsion polymerization method is also preferred. The solvent of the solution polymerization method is not particularly limited and is, for example, an alcohol. The alcohol used in the solvent of the solution polymerization method is, for example, a lower alcohol such as methanol, ethanol or propanol. The amount of solvent used in the polymerization system, as long as it meets the purpose The degree of polymerization of the hydroxymethyl group-containing PVA may be selected in consideration of the chain transfer of the solvent. For example, when the solvent is methanol, the mass ratio of the solvent to all the monomers contained in the polymerization system is {=(solvent)/ (all monomers)} is preferably selected from the range of 0.01 to 10, and more preferably selected from the range of 0.05 to 3.

The polymerization initiator used in the copolymerization of the unsaturated monomer and the vinyl ester monomer represented by the formula (2), as long as it is a conventional polymerization initiator from the polymerization method, for example, an azo initiator The peroxide-based initiator and the redox-based initiator may be selected. An azo initiator, for example: 2,2'-azobisisobutyronitrile, 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis (4-Methoxy-2,4-dimethylvaleronitrile). The peroxide-based initiator is, for example, a percarbonate such as diisopropylperoxydicarbonate, di-2-ethylhexylperoxydicarbonate or diethoxyethylperoxydicarbonate. a compound; a perester compound such as a tertiary butyl peroxy neodecanoate or an α-cumyl peroxy neodecanoate; an ethyl fluorenylcyclohexylsulfonate peroxide; 2,4,4-trimethyl Pentyl-2-peroxyphenoxyacetate; acetoxy peroxide. Potassium persulfate, ammonium persulfate, hydrogen peroxide or the like may be combined as the polymerization initiator as a polymerization initiator. The redox-based initiator is, for example, a polymerization initiator which combines the above-mentioned peroxide-based initiator with a reducing agent such as sodium hydrogen sulfite, sodium hydrogencarbonate, tartaric acid, L-ascorbic acid or Rongalit. The amount of the polymerization initiator to be used varies depending on the type of the polymerization initiator, and therefore it cannot be determined in any way, but it can be selected in accordance with the polymerization rate. For example, when 2,2'-azobisisobutyronitrile or ruthenium peroxide is used as the polymerization initiator, it is preferably 0.01 to 0.2 mol%, more preferably 0.02 to 0.15, based on the vinyl ester monomer. Moer%.

The copolymerization of the unsaturated monomer represented by the formula (2) and the vinyl ester monomer may also be carried out in the presence of a chain transfer agent. Examples of the chain transfer agent include aldehydes such as acetaldehyde and propionaldehyde; ketones such as acetone and methyl ethyl ketone; thiols such as 2-hydroxyethanethiol; and phosphonates such as sodium phosphonate monohydrate. Among them, aldehydes and ketones are suitably used. The amount of the chain transfer agent to be used may be determined depending on the chain transfer coefficient of the chain transfer agent to be used and the degree of polymerization of the hydroxymethyl group-containing PVA. In general, it is preferably 100 parts by mass based on the vinyl ester monomer. It is 0.1 to 10 parts by mass.

The vinyl ester-based copolymer obtained by copolymerization of the unsaturated monomer represented by the formula (2) and the vinyl ester monomer is saponified, whereby the above-mentioned hydroxymethyl group-containing PVA can be obtained. By saponifying the vinyl ester copolymer, the vinyl ester unit in the vinyl ester copolymer is converted into a vinyl alcohol unit. Further, the ester bond derived from the structural unit of the unsaturated monomer represented by the formula (2) is also saponified, and is converted into a structural unit having a 1,3-diol structure represented by the formula (1). Therefore, the hydroxymethyl group-containing PVA can be produced even after the saponification without further performing a reaction such as hydrolysis.

The saponification of the vinyl ester-based copolymer can be carried out, for example, in a state in which the vinyl ester-based copolymer is dissolved in an alcohol or an aqueous alcohol. The alcohol to be used for the saponification may, for example, be a lower alcohol such as methanol or ethanol, preferably methanol. The alcohol used for the saponification may contain, for example, other solvents such as acetone, methyl acetate, ethyl acetate or benzene in a proportion of 40% by mass or less based on the mass. The catalyst used for the saponification is, for example, an alkali metal hydroxide such as potassium hydroxide or sodium hydroxide; an alkali catalyst such as sodium methoxide; and an acid catalyst such as an inorganic acid. The temperature at which saponification is carried out is not limited, but is preferably in the range of 20 to 60 °C. When the colloidal product is precipitated as the saponification proceeds, After the product was pulverized, it was washed and dried to obtain a PVA containing a methylol group. The saponification method is not limited to the aforementioned method, and a conventional method can be applied.

The PVA containing a methylol group may further contain a structural unit represented by the formula (1), a vinyl alcohol unit, and other structural units other than the vinyl ester unit. The other structural unit may, for example, be a structural unit derived from an ethylenically unsaturated monomer copolymerizable with a vinyl ester monomer. Further, it may contain a structural unit which can be copolymerized with the above vinyl ester monomer and derived from an unsaturated monomer which can be converted into a structural unit represented by the formula (1) (not converted into the formula (1) by saponification) The structural unit of the structural unit shown).

In the PVA containing a methylol group, when the molar number of all the structural units constituting the PVA containing a methylol group is 100 mol%, the total of the structural unit, the vinyl alcohol unit, and the vinyl ester unit represented by the formula (1) The proportion is preferably 80% by mole or more, more preferably 90% by mole or more, still more preferably 95% by mole or more, and may be 99% by mole or more.

The above ethylenically unsaturated monomer is, for example, an α-olefin such as ethylene, propylene, n-butene, isobutylene or 1-hexene; acrylic acid and a salt thereof; an unsaturated monomer having an acrylate group; Acrylic acid and its salt; unsaturated monomer having methacrylate group; acrylamide; N-methyl acrylamide, N-ethyl acrylamide, N, N a acrylamide derivative such as dimethyl methacrylate, diacetone acrylamide, acrylamide propyl sulfonic acid and salts thereof, acrylamidopropyl dimethylamine and salts thereof (for example, a 4-grade salt); Methacrylamide; N-methyl methacrylamide, N-ethyl methacrylamide, methacrylamide a methacrylamide derivative such as propanesulfonic acid and its salt, methacrylamidamine dimethylamine and a salt thereof (for example, a 4-grade salt); methyl vinyl ether, ethyl vinyl ether, and n-propyl Vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, tert-butyl vinyl ether, dodecyl vinyl ether, stearyl vinyl ether, 2 Vinyl ethers such as 3-diethoxycarbonyl-1-vinyloxypropane; vinyl cyanide such as acrylonitrile or methacrylonitrile; halogenated vinyls such as vinyl chloride and vinyl fluoride; vinylidene chloride; a vinylidene halide such as vinylidene fluoride; an allyl compound such as allyl acetate, 2,3-diethyloxy-1-allyloxypropane or allyl chloride; maleic acid or itaconic acid An unsaturated dicarboxylic acid such as fumaric acid or a salt or ester thereof; a vinyl mercapto compound such as vinyltrimethoxydecane or an isopropenyl acetate. Among these, the productivity of the optical film is improved by the fact that the stretching can be performed at a higher temperature while the stretchability is improved, and the occurrence of problems such as tensile fracture at the time of production of the optical film is reduced. Good for ethylene. When the PVA containing a methylol group contains an ethylene unit, the molar number of all structural units constituting the PVA containing a methylol group is 100 mol from the viewpoints of the above-described stretchability and temperature at which stretching can be performed. In the case of %, the content of the ethylene unit is preferably from 1 to 4 mol%, particularly preferably from 2 to 3 mol%.

The arrangement order of the structural unit represented by the formula (1), the vinyl alcohol unit, and any other constituent unit in the hydroxymethyl group-containing PVA is not particularly limited, and may be any of random, block, and alternate.

The film of the present invention may contain a plasticizer in addition to the above-mentioned PVA containing a methylol group. Preferred examples of the plasticizer include polyhydric alcohols; and specific examples thereof include ethylene glycol, glycerin, propylene glycol, diethylene glycol, diglycerin, triethylene glycol, and tetraethylene glycol. , trimethylolpropane, etc. . The film of the present invention may contain one or more of these plasticizers. Among these, glycerin is preferred from the viewpoint of the effect of improving the stretchability.

In the film of the present invention, the content of the plasticizer is preferably in the range of 1 to 20 parts by mass, more preferably 3 to 17 parts by mass, per 100 parts by mass of the PVA containing the methylol group. Within the range, it is preferably in the range of 5 to 15 parts by mass. When the content is 1 part by mass or more, the stretchability of the film is further improved. On the other hand, when the content is 20 parts by mass or less, it is possible to suppress the film from being too soft and the workability is lowered.

The film of the invention can be further blended according to requirements: a processing stabilizer such as a filler or a copper compound, a weather resistance stabilizer, a coloring agent, an ultraviolet absorber, a light stabilizer, an antioxidant, an antistatic agent, and a flame retardant. Agents, other thermoplastic resins, lubricants, perfumes, defoamers, deodorants, extenders, strippers, release agents, reinforcing agents, crosslinking agents, anti-mold agents, preservatives, crystallization rate retarders, etc. additive.

In the film of the present invention, the total proportion of the methylol group-containing PVA and the plasticizer is preferably 80% by mass or more, more preferably 90% by mass or more, and still more preferably 95% by mass based on the mass of the film. the above.

The degree of swelling of the film of the present invention is preferably in the range of 160 to 240%, more preferably in the range of 170 to 230%, and particularly preferably in the range of 180 to 220%. When the degree of swelling is 160% or more, it is possible to suppress the crystallization from proceeding extremely, and it is possible to stably stretch to a higher magnification. On the other hand, when the degree of swelling is 240% or less, the dissolution at the time of stretching is suppressed, and stretching can be performed even under conditions of higher temperature. In the present specification, the degree of swelling of the film means the mass of the film immersed in distilled water at 30 ° C for 30 minutes, and is divided by 105 ° C after immersion. The percentage of the value obtained by drying the mass after 16 hours can be specifically measured by the method described later in the examples.

The thickness of the film of the present invention is not particularly limited, and is generally preferably from 1 to 100 μm, more preferably from 5 to 75 μm, particularly preferably from about 10 to 60 μm. If the thickness is too thin, the uniaxial stretching treatment for producing an optical film such as a polarizing film tends to cause tensile fracture. Further, if the thickness is too thick, stretching unevenness tends to occur during the uniaxial stretching treatment for producing an optical film.

The width of the film of the present invention is not particularly limited, and can be determined in accordance with the use of the optical film to be produced and the like. In recent years, from the point of view of the development of large-screen LCD TVs and LCD monitors, it is suitable for such applications if the width of the film is preferably 3 m or more. On the other hand, when the width of the film is too large, it is difficult to uniformly perform the uniaxial stretching itself when the optical film is produced by a practical device, and therefore the width of the film is preferably 7 m or less.

The method for producing the film of the present invention is not particularly limited, and a method for producing a film having a more uniform thickness and width after film formation can be preferably used. For example, it can be produced by using a film forming stock solution in which a film is dissolved in a liquid medium. a membrane-forming stock solution containing one or more of the above-mentioned plasticizers, additives, and surfactants, which are further dissolved in the above-mentioned hydroxymethyl group-containing PVA; A film forming stock solution in which one or more of a plasticizer, an additive, a surfactant, a liquid medium, and the like, which are further contained, and a PVA containing a methylol group are melted. When the film forming stock solution contains at least one of a plasticizer, an additive, and a surfactant, it is preferably The ingredients are uniformly mixed.

The liquid medium used for the preparation of the film forming solution may, for example, be water, dimethyl hydrazine, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, or B. Diol, glycerin, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, trimethylolpropane, ethylenediamine, diethylenetriamine, etc., one or two of these may be used. More than one species. Among these, water is preferred from the point of burden and recycling to the environment.

The volatilization ratio of the film forming solution (the content of volatile components such as a liquid medium removed by volatilization and evaporation at the time of film formation in the film forming stock solution) varies depending on the film forming method, film forming conditions, and the like. In general, it is preferably in the range of 50 to 95% by mass, more preferably in the range of 55 to 90% by mass, and still more preferably in the range of 60 to 85% by mass. When the volatilization rate of the film forming solution is 50% by mass or more, the viscosity of the film forming solution does not become too high, and the filtration and defoaming during the preparation of the film forming solution can be smoothly performed, and the film having less foreign matter and less defects can be obtained. The manufacture becomes easy. On the other hand, since the volatilization rate of the film forming stock solution is 95% by mass or less, the concentration of the film forming stock solution does not become too low, and industrial production of the film is facilitated.

The film forming stock solution preferably contains a surfactant. By including a surfactant, it is possible to suppress the occurrence of film thickness unevenness while improving the film formability, and it is also easy to use a metal roll or a release film for use in a film. When a film is produced from a film forming stock solution containing a surfactant, the film may contain a surfactant. The type of the surfactant is not particularly limited, and an anionic surfactant or a nonionic surfactant is preferred from the viewpoint of peelability from a metal roll or a belt.

For the anionic interfacial activity, for example, a carboxylic acid type such as potassium laurate or a sulfate type such as polyoxyethylene ethyl lauryl ether sulfate or octyl sulfate; dodecylbenzenesulfonate; Sulfonic acid type and the like.

As the nonionic surfactant, for example, an alkyl ether type such as polyoxyethylene oleyl ether or an alkylphenyl group such as polyoxyethyl octylphenyl ether; Ether type; alkyl ester type such as polyoxy-extension ethyl laurate; alkylamine type such as polyoxy-extension ethyl laurylamine ether; alkyl amide type such as polyoxy-extension ethyl laurate decylamine; Polypropylene glycol ether type such as oxygen extended ethyl polyoxypropyl propyl ether; lauric acid diethanolamide, oleic acid diethanolamine, etc.; polyoxyalkylene allylic benzene Allyl phenyl ether type such as poly oxyalkylene allyl phenyl ether.

These surfactants can be used alone or in combination of two or more.

When the film forming stock solution contains the surfactant, the content thereof is preferably in the range of 0.01 to 0.5 parts by mass, more preferably 0.02 to 0.3 mass, based on 100 parts by mass of the PVA containing the methylol group contained in the film forming stock solution. In the range of parts, it is particularly preferably in the range of 0.05 to 0.1 parts by mass. When the content is 0.01 parts by mass or more, film formability and peelability are further improved. On the other hand, when the content is 0.5 parts by mass or less, it is possible to prevent the surfactant from oozing out to the surface of the film to cause blocking, so that workability is lowered.

The film forming method for forming a film using the above-mentioned film forming stock solution may, for example, be a casting film forming method, an extrusion film forming method, a wet film forming method, or a gel film forming method. These film forming methods can be used only in one type or Two or more types are used in combination. In the film forming method, a casting film forming method or an extrusion film forming method is preferable because a film having uniform thickness and width and good physical properties can be obtained. The film formed can be dried or heat treated as needed.

For the case of the specific manufacturing method of the film of the present invention, for example, the following method can be preferably used in the industry: using a slit die, a hopper plate, an I-shaped die, a lip type a film coat or the like, which is uniformly discharged or cast onto the circumferential surface of the heated first roll (or belt) in the most upstream side of the film, so that volatile components are discharged from the film. Or one side of the film cast on the circumferential surface of the first roll (or belt) is evaporated and dried, and then further on the circumferential surface of the heated roll disposed in one or a plurality of rotations disposed on the downstream side thereof After drying, or by further drying in a hot air drying apparatus, the winding is performed by a winding device. It can also be carried out by appropriately combining the drying by the heated roll and the drying by the hot air drying device.

The use of the film of the present invention is not particularly limited. For example, it can be used for a film for pharmaceutical packaging, a base film for hydraulic transfer, a substrate film for embroidery, a release film for artificial marble molding, a film for seed packaging, and a waste container. In the case of the film of the present invention, it is possible to easily produce an optical film excellent in optical characteristics, durability, and shrinkage, and therefore it is preferably used as a preform for producing an optical film. A film (a blank film for optical film production) is used. Such an optical film is, for example, a polarizing film or a retardation film, and is preferably a polarizing film. Such optical thin The film can be produced, for example, by performing a treatment such as uniaxial stretching using the film of the present invention.

The method for producing the polarizing film using the film of the present invention is not particularly limited, and any of the methods conventionally used may be employed. As such a method, for example, the film of the present invention may be subjected to dyeing and uniaxial stretching, or the film of the present invention containing the dye may be subjected to uniaxial stretching. A more specific method for producing a polarizing film is a method of swelling, dyeing, uniaxially stretching, and further performing cross-linking treatment, fixing treatment, drying, and the like. Heat treatment, etc. In this case, the order of each treatment such as swelling, dyeing, cross-linking treatment, uniaxial stretching, and fixation treatment is not particularly limited, and one or two or more treatments may be simultaneously performed. Further, one or two or more of the respective treatments may be performed two or more times.

The swelling can be carried out by immersing the film in water. The temperature of the water immersed in water is preferably in the range of 20 to 40 ° C, more preferably in the range of 22 to 38 ° C, and even more preferably in the range of 25 to 35 ° C. Further, the time of immersion in water is, for example, preferably in the range of 0.1 to 5 minutes, more preferably in the range of 0.5 to 3 minutes. Further, the water immersed in water is not limited to pure water, and may be an aqueous solution in which various components are dissolved, or may be a mixture of water and an aqueous medium.

The dyeing system can be carried out by bringing a dichroic dye into contact with the film. In the case of a dichroic dye, an iodine dye is generally used. The stage of dyeing may be any stage before uniaxial stretching, uniaxial stretching, or uniaxial stretching. Dyeing is generally carried out by immersing the film in a solution (especially an aqueous solution) containing iodine-potassium iodide as a dye bath. Such a dyeing method can also be suitably employed in the present invention. The concentration of iodine in the dyeing bath is preferably in the range of 0.01 to 0.5% by mass, and the concentration of potassium iodide is preferably in the range of 0.01 to 10% by mass. Further, the temperature of the dye bath is preferably 20 to 50 ° C, and the optimum temperature is 25 to 40 ° C.

By performing the crosslinking treatment on the film, it is possible to more effectively prevent the elution of the methyl group-containing PVA to water at the time of wet stretching at a high temperature. From this point of view, the crosslinking treatment is preferably carried out after the treatment of bringing the dichroic dye into contact and before the uniaxial stretching. The crosslinking treatment can be carried out by immersing the film in an aqueous solution containing a crosslinking agent. For the crosslinking agent, one or two or more kinds of boron compounds such as boric acid such as boric acid or borax may be used. The concentration of the crosslinking agent in the aqueous solution containing the crosslinking agent is preferably in the range of 1 to 15% by mass, more preferably in the range of 2 to 7% by mass, still more preferably in the range of 3 to 6% by mass. By the concentration of the crosslinking agent being in the range of 1 to 15% by mass, sufficient stretchability can be maintained. The aqueous solution containing a crosslinking agent may also contain an auxiliary agent such as potassium iodide. The temperature of the aqueous solution containing the crosslinking agent is preferably in the range of 20 to 50 ° C, and particularly preferably in the range of 25 to 40 ° C. By setting the temperature in the range of 20 to 50 ° C, crosslinking can be performed efficiently.

The uniaxial stretching system can be carried out by either a wet stretching method or a dry stretching method. In the case of the wet stretching method, it may be carried out in an aqueous solution containing boric acid, or in the above dye bath or in a fixed treatment bath to be described later. Further, in the case of the dry stretching method, the film may be directly stretched at room temperature, or may be stretched while being heated, or the film after water absorption may be used in the air. Among these, a wet stretching method is preferred, and uniaxial stretching is more preferably carried out in an aqueous solution containing boric acid. In boric acid aqueous solution The concentration of boric acid is preferably in the range of 0.5 to 6.0% by mass, more preferably in the range of 1.0 to 5.0% by mass, particularly preferably in the range of 1.5 to 4.0% by mass. Further, the aqueous boric acid solution may contain potassium iodide, and the concentration thereof is preferably in the range of 0.01 to 10% by mass.

The stretching temperature in the uniaxial stretching is preferably in the range of 30 to 90 ° C, more preferably in the range of 40 to 80 ° C, and particularly preferably in the range of 50 to 70 ° C.

In addition, the stretching ratio in the uniaxial stretching is preferably 6.8 times or more, more preferably 6.9 times or more, and particularly preferably 7.0 times or more from the viewpoint of the polarizing performance of the obtained polarizing film. The upper limit of the stretching ratio is not particularly limited, but the stretching ratio is preferably 8 times or less.

The direction of uniaxial stretching when the long film is uniaxially stretched is not particularly limited, and uniaxial stretching or transverse uniaxial stretching in the longitudinal direction may be employed, but a polarizing film excellent in polarizing performance can be obtained. Preferably, it is uniaxially stretched in the direction of the strip. The uniaxial stretching in the longitudinal direction can be carried out by using a stretching device having a plurality of rollers parallel to each other, and changing the peripheral speed between the rollers. On the other hand, the transverse uniaxial stretching system can be carried out using a tenter type stretching machine.

In the production of the polarizing film, in order to strongly adsorb the dichroic dye (such as an iodine dye) to the film, it is preferred to carry out a fixing treatment. As the fixed treatment bath used for the fixation treatment, one type or two or more types of aqueous solutions containing a boron compound such as boric acid or borax can be used. Further, an iodine compound and a metal compound may be added to the fixed treatment bath as needed. The concentration of the boron compound in the fixed treatment bath is generally preferably from 2 to 15% by mass, particularly preferably from about 3 to 10% by mass. By this concentration In the range of 2 to 15% by mass, the adsorption of the dichroic dye can be made stronger. The temperature of the fixed treatment bath is preferably from 15 to 60 ° C, particularly preferably from 25 to 40 ° C.

The drying conditions are not particularly limited, but it is preferably carried out at a temperature in the range of 30 to 150 ° C, particularly in the range of 50 to 130 ° C. By drying at a temperature in the range of 30 to 150 ° C, a polarizing film excellent in dimensional stability can be easily obtained.

The polarizing film obtained as described above is usually used as a polarizing plate by bonding a protective film which is optically transparent and has mechanical strength on both surfaces or one surface thereof. As the protective film, a cellulose triacetate (TAC) film, a cycloolefin polymer (COP) film, a cellulose acetate butyrate (CAB) film, an acrylic film, a polyester film, or the like is used. In addition, examples of the adhesive to be bonded include a PVA-based adhesive and an urethane-based adhesive. Among them, a PVA-based adhesive is suitable.

The polarizing plate obtained as described above can be used as a component of an LCD by applying an adhesive such as an acrylic resin and then bonding it to a glass substrate. Simultaneously, it may be bonded to a retardation film, a viewing angle enhancement film, a luminance improving film, or the like.

[Examples]

Hereinafter, the present invention will be described in more detail by way of examples, but the invention is not limited by the examples. In addition, each measurement or evaluation method used by the following Examples, Reference Examples, and Comparative Examples is shown below.

Primary structure of PVA

The primary structure of PVA (the content of the structural unit of the modified species, the amount of 1,2-glycol bond, and the degree of saponification) used in the following examples, reference examples, and comparative examples were analyzed by 400 MHz ¹ H-NMR. The solvent used in the ¹ H-NMR measurement used deuterated DMSO.

Film swelling degree

The film obtained in the following examples, reference examples or comparative examples was cut into 1.5 g, and immersed in distilled water at 30 ° C for 30 minutes. After immersing for 30 minutes, the film was taken out, and water on the surface was wiped with a filter paper to obtain a mass "N". Next, the film was dried in a dryer at 105 ° C for 16 hours, and then the mass "M" was obtained. The degree of swelling of the film was calculated from the obtained masses "N" and "M" by the following formula (3).

Swelling degree (%) = 100 × N / M (3)

Film stretchability

From the center portion in the width direction of the film obtained in the following examples, reference examples, or comparative examples, a sample having a width of 5 cm × a length of 8 cm was cut so that the range of the width of 5 cm × the length of 5 cm was uniaxially stretchable. The sample was immersed in pure water at 30 ° C while being uniaxially stretched 1.5 times in the longitudinal direction. Then, while immersing in an aqueous solution (dyeing bath) (temperature: 30° C.) containing iodine at a ratio of 0.03% by mass and containing potassium iodide at a ratio of 3.0% by mass, uniaxially stretching 1.6 times in the longitudinal direction while immersing for 60 seconds (2.4 times as a whole) and adsorbed iodine. Next, while immersing in an aqueous solution (cross-linking bath) containing 30% by mass of zirconium acid and containing potassium iodide in a ratio of 3% by mass (temperature: 30° C.), the uniaxial stretching was 1.1 times in the longitudinal direction (total 2.6 times). Furthermore, while immersing in an aqueous solution (stretching bath) containing boric acid in a ratio of 4% by mass and potassium iodide in a ratio of 6% by mass, uniaxial stretching is performed in the longitudinal direction to Before the cutting, the magnification of the length at the time of cutting with respect to the length of the film before stretching was set as the critical stretching ratio. However, in terms of the temperature of the stretching bath, the critical stretching ratio was measured by changing the temperature from 1 ° C at an appropriate temperature, and the temperature at which the critical stretching ratio became the highest was selected.

Optical properties of polarizing film (dichroic ratio)

(1) Determination of penetration rate Ts

In the center portion of the polarizing film obtained in the following examples, reference examples, or comparative examples, two 2 cm samples were taken in the longitudinal direction of the polarizing film, and a spectrophotometer with an integrating sphere (manufactured by JASCO Corporation) was used. V7100"), according to JIS Z 8722 (measurement method of object color), the illuminance correction of the visible light region of the C light source and the 2° field of view is performed, and the light is measured at a tilt of +45° with respect to the longitudinal direction for one sample. The penetration rate and the transmittance of the light at an inclination of -45° were obtained, and the average value Ts1 (%) was obtained. The same was carried out for the other sample, and the transmittance of light at an inclination of +45° and the transmittance of light at an inclination of -45° were measured, and the average value Ts2 (%) of these was obtained. Ts1 and Ts2 are averaged by the following formula (4) to give a transmittance Ts (%) of the polarizing film.

Ts=(Ts1+Ts2)/2 (4)

(2) Determination of the degree of polarization V

In the same manner as in the case of the above-mentioned "(1) Measurement of the transmittance Ts", the transmittance of the light is superimposed so that the longitudinal direction thereof is parallel. T∥(%) is a transmittance V(%) obtained by the following formula (5) by the transmittance T⊥(%) of the light when it is superposed perpendicularly to the longitudinal direction.

V={(T∥-T⊥)/(T∥+T⊥)} ^1/2 ×100 (5)

(3) Calculation of dichroic ratio when the penetration rate is 44%

In each of the following examples, reference examples, and comparative examples, the concentration of iodine in the dyeing bath was changed to 0.02 to 0.04 mass%, and the concentration of potassium iodide was changed in the range of 2.0 to 4.0 mass% four times. The same operation was carried out by the concentration of iodine: the concentration of potassium iodide = 1:100), and four polarizing films having different adsorption amounts of the dichroic dyes of the polarizing film produced in each of the examples, the reference examples, and the comparative examples were produced. The transmittance Ts (%) and the degree of polarization V (%) were obtained by the above methods for each of the four polarizing films, and the transmittance Ts (%) was plotted on the horizontal axis and the polarization V (%) was used as the vertical. In the respective embodiments, the reference examples and the comparative examples, the total of the transmittance Ts (%) and the degree of polarization V (%) of the polarizing film obtained by each of the examples, the reference examples, and the comparative examples are also included. Five points are plotted on the graph to obtain an approximate curve, and from this approximate curve, the degree of polarization V ₄₄ (%) when the transmittance Ts (%) is 44% is obtained.

From the obtained degree of polarization V ₄₄ (%), the dichroic ratio at a transmittance of 44% was obtained by the following formula (6), and it was used as an index of the polarizing performance.

The dichroic ratio at a transmittance of 44% = log (44/100-44/100 × V ₄₄ /100) / log (44 / 100 + 44 / 100 × V ₄₄ / 100) (6)

Durability of polarizing film

Two sheets of the polarizing film obtained in the following examples, reference examples, or comparative examples were individually fixed to a metal frame, laminated to a crossed Nichol prism, and the initial (0 hour) was measured by a spectrophotometer. Absorbance A (value at wavelength 610). Further, the polarizing film fixed to the metal frame was stored in a gas environment of 60 ° C ‧90% RH for 8 hours, and then laminated to a crossed Nicol prism to measure by a spectrophotometer. The absorbance B after 8 hours (the value at a wavelength of 610 nm). The value of the absorbance B/absorbance A × 100 was made a residual ratio (an index derived from the color fading of the PVA-iodine complex).

Contraction force of polarizing film

The center portion of the polarizing film obtained in the following examples, reference examples, or comparative examples was a rectangular sample having a length of 12 cm in the longitudinal direction of the polarizing film and 1.5 cm in the width direction, and the temperature was 20 ° C and the relative humidity was 20%. The condition was adjusted for 18 hours. Then, the sample was fixed to the Autograph "AG-X" manufactured by Shimadzu Corporation at a temperature of 40 ° C and a relative humidity of 5% at a temperature of 40 ° C and a relative humidity of 5 mm. The speed was stretched in the longitudinal direction, and when the tension reached 2 N, the stretching was stopped and maintained, and the tension after the temperature was raised to 80 ° C for 4 hours in this state was measured, and this was used as the contraction force of the polarizing film.

[Example 1]

(1) The following aqueous solution was used as a film forming stock solution, dried on a metal roll at 80 ° C, and the obtained film was heat-treated at a predetermined temperature for 1 minute in a hot air dryer to adjust the degree of swelling to 200% to produce a film having a thickness of 30 μm, the aqueous solution comprising: copolymerization obtained by copolymerizing vinyl acetate with 1,3-diethoxymethoxy-2-methylenepropane at a polymerization temperature of 40 ° C 100 parts by mass of a hydroxymethyl group-containing PVA shown in Table 1, 10 parts by mass of glycerin as a plasticizer, and 0.1 parts by mass of polyoxyalkylethyl lauryl ether sulfate as a surfactant, obtained by saponification, Further, the content of PVA containing a methylol group was 10% by mass.

Using the obtained film, the stretchability was evaluated by the above method. will The results are shown in Table 1.

(2) From the center portion in the width direction of the film obtained in the above (1), a sample having a width of 5 cm and a length of 8 cm was cut so that the range of the width of 5 cm × the length of 5 cm was uniaxially stretchable. The sample was immersed in pure water at 30 ° C while being uniaxially stretched 1.5 times in the longitudinal direction. Then, while immersing in an aqueous solution (dyeing bath) (temperature: 30° C.) containing iodine at a ratio of 0.03% by mass and containing potassium iodide at a ratio of 3.0% by mass for 60 seconds, the uniaxial stretching was 1.6 times in the longitudinal direction ( 2.4 times as a whole) and iodine adsorption. Next, while immersing in an aqueous solution (cross-linking bath) containing 30% by mass of boric acid and containing potassium iodide in a ratio of 3% by mass (temperature: 30° C.), the uniaxial stretching was 1.1 times in the longitudinal direction (total 2.6 times). Furthermore, it is immersed in an aqueous solution (stretching bath) containing boric acid in a ratio of 4% by mass and potassium iodide in a ratio of 6% by mass (the critical draw ratio obtained by the above-mentioned "stretchability of the film" is the highest temperature) It is uniaxially stretched in the longitudinal direction until it is 0.2 times lower than the critical stretching ratio.

Thereafter, the mixture was immersed in an aqueous solution (washing bath) (temperature: 30° C.) containing potassium iodide at a ratio of 3% by mass for 5 seconds, and finally dried at 60° C. for 4 minutes to produce a polarizing film. Further, a plurality of the same polarizing films are produced, so that each measurement or evaluation can be performed.

Using the obtained polarizing film, the optical characteristics (dichroic ratio), durability, and shrinkage force of the polarizing film were measured or evaluated by the above method. The results are shown in Table 1.

[Example 2, Reference Example 1, Comparative Examples 1 and 2]

In addition to the use of: by vinyl acetate and 1,3-diethoxy The hydroxymethyl group-containing PVA shown in Table 1 obtained by saponification of a copolymer obtained by copolymerization of a base-2-methylenepropane at a polymerization temperature of 20 ° C (Example 2); by using vinyl acetate The hydroxymethyl group-containing PVA obtained in Table 1 obtained by saponification of a copolymer obtained by copolymerizing 1,3-diethoxycarbonyl-2-methylenepropane at a polymerization temperature of 60 ° C (Reference Example) 1); an unmodified PVA shown in Table 1 obtained by saponifying a polymer obtained by polymerizing vinyl acetate at a polymerization temperature of 60 ° C (Comparative Example 1); and by using vinyl acetate as A film and a polarizing film were produced in the same manner as in Example 1 except that the polymer obtained by the polymerization at a polymerization temperature of 40 ° C was saponified and the unmodified PVA (Comparative Example 2) shown in Table 1 was used as the PVA. Each measurement or evaluation was performed.

The results are shown in Table 1.

As is apparent from the above results, it is possible to easily produce an optical film excellent in optical characteristics, durability, and shrinkage in accordance with the films of Examples 1 and 2 which satisfy the rules of the present invention.

Claims (6)

A film comprising a hydroxymethyl group-containing vinyl alcohol polymer comprising a vinyl alcohol unit and a structural unit represented by the following formula (1), and 1, The amount of 2-diol bond is 1.5 mol% or less. The film of claim 1, wherein the content of the structural unit represented by the formula (1) in the methylol group-containing vinyl alcohol polymer is 0.1 to 2 mol%. The film of claim 1 or 2, wherein the hydroxymethyl group-containing vinyl alcohol polymer has a degree of saponification of 95 mol% or more. The film according to any one of claims 1 to 3, which is a preform material film for optical film production. The film of claim 4, wherein the optical film is a polarizing film. A method of producing an optical film having a step of uniaxially stretching using a film as claimed in claim 4 or 5.